Whenever possible, download from the Google Play Store to minimize the risk of malware.
There is no widely recognized or official application specifically named "Yaps209 sign apk." This name likely refers to a specific or a package name (like a build identifier) of an existing APK signing tool. Download Yaps209 sign apk
Are you trying to that you developed, or are you trying to re-sign a modified app for personal use? apk-signer - Apps on Google Play Whenever possible, download from the Google Play Store
A popular app that lets you sign APK files directly on your phone or tablet. It supports modern V2 signing schemes and allows you to manage keystores. apk-signer - Apps on Google Play A popular
If you are looking for authentic, untouched apps, APK Mirror is a highly reputable source that verifies all signatures before publishing. Safety Checklist for Unknown APKs
Be wary if the app asks for excessive permissions, like access to your contacts or SMS, that it doesn't need for signing files.